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The Porsche Taycan's Two-Speed Gearbox

104 points by jbredeche 7y ago

mywittyname 7y ago
I'm surprised ZF/Porsche didn't turn this into an eCVT, as an eCVT (a la Prius) has probably the same complexity, but with the added benefit of having more ratios. I suspect it would also reduce shock loads on the transmission as a result of shifting. I wish the article would have gone into this, because I suspect Porsche said no more for marketing reasons rather than technical ones, as CVTs are universally hated in car performance circles.
- aidenn0 7y ago
  Wouldn't an eCVT require an additional motor?
  - mywittyname 7y ago
    Yes, but only two small ones to control the rotational speed of the ring / planet gears.
    - aidenn0 7y ago
      I'm not convinced it's in the same ballpark of complexity as a 2-speed gearbox, which would need just a simple two-way friction clutch.
- efraim 7y ago
  A CVT can't handle as much torque as a gear-based transmission.
  - ferongr 7y ago
    The e-CVT has nothing to do with actual CVTs, it's a planetary "torque split" gearbox that's very robust.
  - rhinoceraptor 7y ago
    That could simply be due to the fact that CVTs have never been really used and developed for high performance applications, since car enthusiasts hate them. But there was an F1 car with a CVT before they were banned.
  - mywittyname 7y ago
    CVT != eCVT An eCVT is a planetary gearbox which uses a pair of electric motors to control the rotational speed of the ring and planetary gears to achieve an overall gear ratio anywhere between a minimum and maximum ratio. It's largely the same thing as what this two-speed gearbox is, but it leverages electric motors to provide a smooth transition between two ratios, instead of using (presumably) a set of clutches and auxiliary gears to select one of two fixed ratios. This is why this question jumped out at me immediately. On the surface, they are going with a really, really archaic, complex design over a more simple, all-electric design which is ideally suited for their application. I can't help but think ZF started with an eCVT, then retrofited it back to being a two-speed. They must have had a good reason for this. And I wonder if it's a patent/license issue, or if there's some technical reason this wouldn't work. And I'm disappointed the article doesn't go into details on this.
- madmulligan 7y ago
  The main advantage of the eCVT is the ability to seamlessly combine the power from two motor-generator units and an ICE (as in the Prius) while holding the ICE in the RPM range you want it. Here, there is only one electric motor and keeping it at a certain RPM range (other than below it's max) isn't really important. While a CVT will get you smooth ratio changes, you are still constrained by a minimum and maximum gear ratio, a range which is relatively small compared to this kind of two speed (in this case you can have two gear ratios that are super far apart, as an electric motor makes the same torque regardless of the RPM, unlike an ICE, where you want your gear ratios close to help stay in the powerband). As for CVT's being universally hated in performance circles, they're only universally hated by the same kind of people that hate flappy paddle dual clutch transmissions, i.e people who don't care or know what is actually faster, more reliable, and more efficient in different use cases, but only care about a clutch and an H-pattern shifter.
  - mywittyname 7y ago
    > and keeping it at a certain RPM range (other than below it's max) isn't really important. Yeah it is, because electric motors have RPM bands where they are most efficient. The whole point of a adding a two-speed transmission in the first place was to increase efficiency, range, and top speed. If they managed a 5% improvement with a two-speed, I'm betting they could at least double that with an eCVT.
- whalesalad 7y ago
  CVT transmissions can’t handle the power. They’re also universally hated by everyone except people who merely use a car to get from A to B. A Porsche owner is the polar opposite of someone who would tolerate a CVT.
  - cat199 7y ago
    someone this close minded would likely not be considering electric in the first place (and would probably whine about porches being mostly v6 and not v8/10/12)
    - whalesalad 7y ago
      Close minded? Huh. You won’t find a CVT in anything but a budget economy vehicle. If you want performance, you don’t want a CVT. If you want to prioritize efficiency over everything else (including reliability), a CVT is fine.
      - rodgerd 7y ago
        https://en.wikipedia.org/wiki/Williams_FW15C https://en.wikipedia.org/wiki/Williams_FW15C
      - enragedcacti 7y ago
        CVTs grant you the ability to maintain peak power at all speeds for acceleration and you don't have any losses to shifting. If you look at recent Civics for example Sport trims with more horsepower and a manual trans will lose out or tie CVT models in 0-60 and 1/4 mile times despite the CVTs having bad launch characteristics. And this doesn't even touch on how torquey they can feel at higher speed relative to a standard trans at the same HP. I won't question your claims about reliability but CVTs are actually pretty performant within their segment, they just dont make the Vroom Vroom shifty noises that some car enthusiasts equate to performance. The primary issue with CVTs (as others have mentioned) is that they can't be strapped to engines that make more than ~200 HP.
      - cat199 7y ago
- rhinoceraptor 7y ago
  It seems like the advantage of a CVT only really apply to internal combustion engines since they can only really go from about 500 to 8,000 rpm, and in that range they only have peak power or peak efficiency in small ranges. EV motors can go from 0 to 18,000 rpm.
aidenn0 7y ago
FWIW the original Tesla roadster was also a 2 speed, but they dropped the gearing as soon as they could meet their original top-speed without it.
- rconti 7y ago
  Yeah, and it was apparently prone to breaking (I learned this from Googling just now). I was pretty sure I drove a 2-speed Roadster back in the day, but wanted to confirm that actually made it to production -- it did. (The Roadsters I drove were Tesla-owned but I'm pretty sure they were full production models). The more things change, the more they stay the same. I remember Tesla being laughed at for this whole overpriced roadster thing, then because their transmissions were breaking, then because the 'fix' was to produce a "crippled" 1-speed car because they couldn't figure out how to make a transmission that didn't break. And now, 10 years later, I own a 1-speed one, and, miraculously, the whole thing works on a real sedan, not just a kit car.
gleglegle 7y ago
It's a little surprising that even with a two-speed Gearbox the Taycan has neither better range nor low range 0-60 acceleration than the Tesla P100D (which has the same size battery). Obviously spec comparisons aren't the whole story and the handling and high-range acceleration may be better on the Taycan. Looking forward to seeing more comparisons and already glad to see more EV models in this category. Edited incorrect comment about top speed.
- milkytron 7y ago
  According to the article: > It’s programmed to shift between its two speeds at 43 mph, though the computer can be programmed to make the change at different points based on the route, topography, or the distance the driver hopes to cover before plugging in. I wonder if that shift point has anything to do with the slower acceleration. I'd imagine it would make a small difference. As for the top speed, I believe Tesla is limited to 155mph and the Taycan is reported to be limited at 161mph. So the Taycan is actually faster, but I'm not sure how much it matters since both are limited by the software.
  - minhazm 7y ago
    Model S top speed is 163 mph.
- Mikeb85 7y ago
  Porsches have never really been about straightline speed. Always about overall performance and a sports-car feeling. I'm guessing they optimized things like power, gearing and weight placement to offer good acceleration through a range of speeds with amazing handling and decent range at speed.
  - rconti 7y ago
    True, and the Taycan may well be a better car in many ways. But a discussion of the gearbox has nothing to do with handling or sports car feeling. I'm wondering what we're missing here. 5% efficiency improvement at high speeds isn't anything to write home about today. The transmission is a known quantity -- it's just gears, it won't get more efficient as they develop it. The efficiency of the whole system (battery/drivetrain/regen/motor/aero/etc) can be optimized quite a bit going forward, but if the 2-speed transmission will only ever get us a 5% increase, I'm not sure it's worth the added weight and complexity. Obviously Porsche knows what they're doing, and it may be about thermal management on the Autobahn more than about outright efficiency, but I'm skeptical. If this were 2010 I'd say "yeah, obviously Porsche knows something about building a real sedan that you can take on a real highway trip, Tesla has no idea what they're doing". But, having produced actual sedans that actually work, and Porsche going with a more complicated system for 5%.. I don't know what I'm missing.
elihu 7y ago
Seems logical. I think most manufacturers have just decided that they'd rather use an over-sized motor than deal with a transmission, but if you're willing to tolerate a more complicated drive-train you get more usable power with less weight. Using a transmission might get weird if you have multiple motors, though. For instance, it would be odd to have the front wheels in one gear and the rear wheels in a different gear, or the right rear wheel in a different gear than the left rear wheel.
- jameskilton 7y ago
  From what I've read, the AWD versions of the Model 3 (possibly others) actually do this (different ratios in the front and back). As the article says, Tesla had a hard time building a transmission that wouldn't tear itself apart under the torque of the electric motors. So, they put the front and back motors at different ratios. The back motor is used at lower speeds, and the front motor kicks in at higher speeds.
  - rconti 7y ago
    I'm not sure about the higher speeds vs lower speeds thing. Anyway, Tesla knows the gear ratios in both units, they can apply power as necessary to get the exact torque split the computer wants.
  - elihu 7y ago
    That makes sense for fixed-gear setups; I guess they just have to make sure that the lower-geared motor can spin at high enough RPM that it's not limiting the overall maximum speed. (Or perhaps they can use a freewheel mechanism, but that defeats using that motor for electronic braking.) Having multiple motors each with their own switchable-gear transmission on the other hand might get hard to justify in terms of complexity.
AgloeDreams 7y ago
As I understand it, this gearbox type is key on Porche's intent to make it able to maintain performance over use rather than overheat, notably it improves acceleration and efficiency at high speed. I would expect the Taycan to use less energy to maintain 150mph.
- johnvanommen 7y ago
  Ah, that makes sense. So that it can cruise at high speeds efficiently.
- nraynaud 7y ago
  don't you have a ton of cooling air at 150mph?
  - AgloeDreams 7y ago
    It's about efficiency at various speeds, plus having to intake more air to cool more things increases drag, the best way to improve cooling performance is to improve power use in the first place.
mprovost 7y ago
Interesting fact about ZF: it was founded in 1915 to make gearboxes for zeppelins.
- johnvanommen 7y ago
  TIL: "ZF Friedrichshafen is more than 90% owned by the Zeppelin Foundation, which is largely controlled by the town of Friedrichshafen."
baybal2 7y ago
Direct drive BLDCs have enough torque to drive anything under 1t. A split torque design doubles that to 2t. Tiny Chinese EVs have no problems with autobahn speeds for any amount of time.
jaclaz 7y ago
Once upon a time there were cars with a "normal" 4 speed (+reverse) gearbox and an added "overdrive" box (that if I recall correctly could only be used in 3rd and 4th gear), surely there were a few Triumph's and some Volvo station wagons, they had a button/switch on the gear stick that activated it electrically. https://en.wikipedia.org/wiki/Overdrive_(mechanics) https://en.wikipedia.org/wiki/Overdrive_(mechanics) This device (with all the possible evolutions in these 30 or 40 years) sounds a lot like this "overdrive" box.
- kwhitefoot 7y ago
  Loads of cars had an overdrive and it made a significant difference to fuel economy at high speed. I think the difference here is that the Taycan has a kind of automatic gearbox that can operate while under hard acceleration whereas, as far as I remember, you only pushed the overdrive button when you had reached cruising speed.
  - jaclaz 7y ago
    Yes, that is part of the evolutions I mentioned, what I meant essentially was saying that a two speed gearbox (electrically/hydraulically operated) reminds me more an overdrive box (which is actually a two speed gearbox electrically/hydraulically operated) than an actual 4/5/6 speed manual or automatic gearbox. The actual use of the old overdrive was to lower revs of the engine (please read as save fuel) at a given speed, or (I know, not the actual intended use) to increase top speed, which is exactly what the new Taycan gearbox seemingly is used for (automatically, not manually, of course). I remember a diesel Volvo station wagon (must have been a volvo 240 or 244) where in order to overtake someone at 120-130 kmh, the procedure was: 1) turn A/C off 2) accelerate as much as possible in 4th gear 3) push the override button that gave just a little more speed.
nickhalfasleep 7y ago
In dual-motor (front, rear) Tesla vehicles, each motor is on a different gear ratio for optimal power bands.
- adrianmonk 7y ago
  I wonder if this is part of why their dual-motor models get better range. I could see it being better for regenerative braking, too.
  - robotresearcher 7y ago
    Double the regenerative braking is why they get better range, I bet, despite being heavier.
    - kwhitefoot 7y ago
      The two motors in a Model S are different ratings. It seems that at cruising speed the car can choose the most efficient one to use and let the other one 'freewheel'. Two motors probably gives better control over regen and certainly over braking but the regen rate seems to be determined by the battery, inverter, and design decisions. In my 2014 Model S 70D the maximum regen is about 50 kW, at least that's what the display shows, but the motors can develop at least 250 kW. I suspect it is also limited for safety reasons, 250 kW of braking would give deceleration of about the same magnitude as the maximum acceleration. At 100 kph (27.8 m/s) the car has an energy of about 1.62 MJ so at 250 kW it would come to a stop in 6.5 seconds. Actually my car does 0 to 100 kph in about 5.6 seconds so it clearly produces more than 250 kW. Sorry for rambling on, your comment set me thinking and then I just had to check my working.
  - adrr 7y ago
    Not sure on the S or X but my model 3 AWD has less range than RWD. AWD is quicker by 10%.
    - driverdan 7y ago
nraynaud 7y ago
just to be sure: should I be in awe in front of a 2 speeds automotive gearbox from a 100 years old manufacturer? it's been a few minutes and I still don't feel the tingling.
kazinator 7y ago
> Multispeed transmissions must be robust to deal with the massive amounts of torque that electric motors can generate in a very short period of time, says Shashank Sripad, a mechanical engineer also from Carnegie Mellon. Put a manual clutch on it; problem solved. Manual boxes can be built strong. Then make it at least a 3 speed so there is a decent H pattern there from the stick user's perspective, and so that the ratio isn't so large (it's like around 2X change¹, supposedly! That means the motor's RPM has to drop by by half on upshift and double on downshift.) 3 speeds could use a 1.44 step. 1 3 | | +-- | \ 2 R = V/I --- 1. Source: this article claims the gears are 16:1 and 8.05:1. https://jalopnik.com/an-extremely-detailed-look-at-the-porsche-taycans-engin-1837802533 https://jalopnik.com/an-extremely-detailed-look-at-the-porsc...
- GhostVII 7y ago
  If you put a manual gearbox in it, I bet a single bad shift would tear it apart with all that torque at low RPM. Also would probably kill the clutch unless you are a really good driver, and it is hard to shift when you can't hear the engine RPM. And I don't think manual gearboxes are any stronger than a well built automatic but I have nothing to back that up except intuition.
  - kazinator 7y ago
    > it is hard to shift when you can't hear the engine RPM. A third-rate hardware tinkerer could come up with a circuit that makes a motorboating sound from a speaker at the engine RPM. That could be heard just during shifting activity, like when the clutch is out. > Also would probably kill the clutch. It would require a special clutch design. The clutch is not needed when starting, of course, because since the motor can generate torque right from zero RPM, the transmission can be engaged. A clutch mechanism needed when changing gears due to the mismatch in speeds that needs to be bridged. The existing two-speeder must have something serving as a clutch, just not a manually operated one. Speaking at torque at zero RPM; can't that be modulated down somehow? Surely there must be some way of managing the motor to bring in torque gently. This must be happening already, right? I mean, electric cars don't burn rubber each time they get moving. > I don't think manual gearboxes are any stronger than a well built automatic That's easy; just define the requirements for "well built" so that it is so, and don't care about weight, size, and other things. The automatic transmission from a bus is probably stronger than the manual in an econobox car.
phkahler 7y ago
Aside from not providing much of any performance benefit, this will introduce difficulty coordinating regenerative braking through the shift point. One of my former employers had a group trying really hard to make a 2-speed for EVs make sense. It just doesn't. If there is an efficiency gain, it's probably better to throw the extra money and weight into the motor. An exception might be if you want to cruise at 120+ mph for long distances, but that's not realistic.
- youeseh 7y ago
  Which part of cruising at 120+ mph for long distances is not realistic?
  - NDizzle 7y ago
    Long distances?
  - sdfswfsafaswf 7y ago
    1. outside Germany, cops 2. power scales as v^3 destroying range.
    - Gibbon1 7y ago
      We shouldn't lose sight of #3. 3. This is a toy we're talking about here.
  - lazyjones 7y ago
    I eagerly await to see the Taycan's range at 120+ mph. evcalc.ch suggests it would be around 164 Km for 200 Km/h (Turbo S).
- GhostVII 7y ago
  Why don't you think there will be much performance benefit? The Porsche taycan is much faster accelerating than any Tesla at high speeds, probably due to the two speed gearbox. I don't think it is an efficiency thing, electric motors just start loosing power after a certain rpm, and a gearbox helps with this.
woodandsteel 7y ago
According to the article, two-speed transmissions can increase range about 5%. That is important because batteries are so expensive. However, battery prices are falling rapidly. They dropped 35% in 2018 alone. That being the case, I am guessing most ev manufacturers will stick with single-speed powertrains, and focus their technological efforts elsewhere.
Whatarethese 7y ago
Currently there is no reason to put transmissions into EV's. More money should be put into the improvement of electric motors and battery tech. People care about range and reliability. While acceleration is awesome, Tesla can already achieve sub 2.5s 0-60 which is more than most anyone can handle. Adding a transmission to an EV just adds one more thing to fail and replace fluid every few years.
- compiler-guy 7y ago
  Are saying that Porsche--which is spending billions of dollars on the Taycan and its transmission--is doing this for no good reason? "People care about range and reliability."--Certainly some, perhaps most people, do. And Tesla serves that market very well. But that isn't Porsche's market. Porsche's target market cares a lot about handling, and performance in track-like conditions.
  - Dylan16807 7y ago
    > Are saying that Porsche--which is spending billions of dollars on the Taycan and its transmission--is doing this for no good reason? Yes, they are. They are saying that "better on a track" is a bad reason, and "it makes more money" is a bad reason. That is not a claim that Porsche is incorrectly engineering to reach their goal, or doing anything unprofitable. It's an opinion.
    - GhostVII 7y ago
      In what way is "better on track" a bad reason? Lots of cars have features which are only really useful on a track, are all of these cars needlessly complex?
      - Dylan16807 7y ago
        A lot of people would say yes, and I would not call them objectively wrong to have that opinion.
    - compiler-guy 7y ago
compiler-guy 7y ago
The level of hubris here is pretty high. "No reason"? "No performance benefit"? Porsche is spending billions of dollars to bring a very high performance track-focused sports-sedan to the market. Hundreds of extremely good engineers are getting paid millions of dollars to figure this problem out. I'm sure the transmission is a giant set of engineering tradeoffs (what project isn't), and maybe it won't work out and will end up being the wrong solution. But it can't be so obvious that random Joe-and-Jane HackerNews know the answer off the top of their heads and Porsche doesn't after all the resources it has spent to figure out the problem.
- navigatesol 7y ago
  There are people on this site and others that truly believe Elon Musk is the smartest engineer on the planet, and by definition his technology is always the best.
  - deleted 7y ago
    [deleted]
  - erikpukinskis 7y ago
    Please keep your conversations with imaginary people to yourself. There are actual comments here from actual people you can respond to if you’re interested in participating.
  - Gibbon1 7y ago
    Well certainly. But behind that guy is a lot of compentent and professional engineers and techs doing the actual work.
- gleenn 7y ago
  I understand your sentiment. I'd like to add the fact that the original Tesla was a two-speed, or perhaps it was the original design for the Model S, but they scrapped it for simplicity IIRC.
  - ztjio 7y ago
p1mrx 7y ago
> comes mated to a motor with a maximum power rating of 140 kW Is that a typo? The Chevy Bolt and Hyundai Kona both have 150 kW motors, and Teslas start above 200 kW.
- STRML 7y ago
  They don't have any actual inside information about the Taycan, so they switch to talking about the ZF transmission.
ravedave5 7y ago
Porsche has to have reasons for using a gearbox but I don't think this article espouses them. The points they hit on are where Tesla's as good or better, so there must be other good reasons.
userbinator 7y ago
Many years ago I remember reading about EV conversions, and besides direct drive or keeping the existing multispeed (manual) transmission, one of the other relatively popular options was a Chevrolet Powerglide with the torque converter removed. This is a two-speed automatic from the 1950s that's known for being simple and very strong, and remains quite popular for drag racing. I suspect its popularity for EV conversions also arises from being able to handle the huge amount of torque an electric motor can exert, and the better performance of 2 speeds, so it's interesting to see Porsche also choosing a 2-speed auto for its EV.
FullyFunctional 7y ago
What a load of bullshit. The article is making a merit out of a clutch to cover for their failing. I had to stop reading after ridiculous statements like “that 5 percent range improvement can save significant money as battery capacity” - riiiight it can save ... 5%. I’d rather pay more for the battery and save of the maintenance down the road. Serious Wired, how much did they pay you for this?
rukuu001 7y ago
I'm amazed they spent all that R&D loot and then called it 'Taycan' - I can't decide if it sounds more like 'toucan' or 'trashcan'. FWIW the Wikipedia article[0] on the car has this to say about the name: > The name Taycan, roughly translates from Turkish as "lively young horse" in reference to the steed of the Stuttgart coat of arms on the Porsche crest. [0] https://en.wikipedia.org/wiki/Porsche_Taycan https://en.wikipedia.org/wiki/Porsche_Taycan

104 points by jbredeche 7y ago

I'm surprised ZF/Porsche didn't turn this into an eCVT, as an eCVT (a la Prius) has probably the same complexity, but with the added benefit of having more ratios. I suspect it would also reduce shock loads on the transmission as a result of shifting. I wish the article would have gone into this, because I suspect Porsche said no more for marketing reasons rather than technical ones, as CVTs are universally hated in car performance circles.

aidenn0 7y ago
Wouldn't an eCVT require an additional motor?
- mywittyname 7y ago
  Yes, but only two small ones to control the rotational speed of the ring / planet gears.
  - aidenn0 7y ago
    I'm not convinced it's in the same ballpark of complexity as a 2-speed gearbox, which would need just a simple two-way friction clutch.
efraim 7y ago
A CVT can't handle as much torque as a gear-based transmission.
- ferongr 7y ago
  The e-CVT has nothing to do with actual CVTs, it's a planetary "torque split" gearbox that's very robust.
- rhinoceraptor 7y ago
  That could simply be due to the fact that CVTs have never been really used and developed for high performance applications, since car enthusiasts hate them. But there was an F1 car with a CVT before they were banned.
- mywittyname 7y ago
  CVT != eCVT An eCVT is a planetary gearbox which uses a pair of electric motors to control the rotational speed of the ring and planetary gears to achieve an overall gear ratio anywhere between a minimum and maximum ratio. It's largely the same thing as what this two-speed gearbox is, but it leverages electric motors to provide a smooth transition between two ratios, instead of using (presumably) a set of clutches and auxiliary gears to select one of two fixed ratios. This is why this question jumped out at me immediately. On the surface, they are going with a really, really archaic, complex design over a more simple, all-electric design which is ideally suited for their application. I can't help but think ZF started with an eCVT, then retrofited it back to being a two-speed. They must have had a good reason for this. And I wonder if it's a patent/license issue, or if there's some technical reason this wouldn't work. And I'm disappointed the article doesn't go into details on this.
madmulligan 7y ago
The main advantage of the eCVT is the ability to seamlessly combine the power from two motor-generator units and an ICE (as in the Prius) while holding the ICE in the RPM range you want it. Here, there is only one electric motor and keeping it at a certain RPM range (other than below it's max) isn't really important. While a CVT will get you smooth ratio changes, you are still constrained by a minimum and maximum gear ratio, a range which is relatively small compared to this kind of two speed (in this case you can have two gear ratios that are super far apart, as an electric motor makes the same torque regardless of the RPM, unlike an ICE, where you want your gear ratios close to help stay in the powerband). As for CVT's being universally hated in performance circles, they're only universally hated by the same kind of people that hate flappy paddle dual clutch transmissions, i.e people who don't care or know what is actually faster, more reliable, and more efficient in different use cases, but only care about a clutch and an H-pattern shifter.
- mywittyname 7y ago
  > and keeping it at a certain RPM range (other than below it's max) isn't really important. Yeah it is, because electric motors have RPM bands where they are most efficient. The whole point of a adding a two-speed transmission in the first place was to increase efficiency, range, and top speed. If they managed a 5% improvement with a two-speed, I'm betting they could at least double that with an eCVT.
whalesalad 7y ago
CVT transmissions can’t handle the power. They’re also universally hated by everyone except people who merely use a car to get from A to B. A Porsche owner is the polar opposite of someone who would tolerate a CVT.
- cat199 7y ago
  someone this close minded would likely not be considering electric in the first place (and would probably whine about porches being mostly v6 and not v8/10/12)
  - whalesalad 7y ago
    Close minded? Huh. You won’t find a CVT in anything but a budget economy vehicle. If you want performance, you don’t want a CVT. If you want to prioritize efficiency over everything else (including reliability), a CVT is fine.
    - rodgerd 7y ago
      https://en.wikipedia.org/wiki/Williams_FW15C https://en.wikipedia.org/wiki/Williams_FW15C
    - enragedcacti 7y ago
      CVTs grant you the ability to maintain peak power at all speeds for acceleration and you don't have any losses to shifting. If you look at recent Civics for example Sport trims with more horsepower and a manual trans will lose out or tie CVT models in 0-60 and 1/4 mile times despite the CVTs having bad launch characteristics. And this doesn't even touch on how torquey they can feel at higher speed relative to a standard trans at the same HP. I won't question your claims about reliability but CVTs are actually pretty performant within their segment, they just dont make the Vroom Vroom shifty noises that some car enthusiasts equate to performance. The primary issue with CVTs (as others have mentioned) is that they can't be strapped to engines that make more than ~200 HP.
    - cat199 7y ago
rhinoceraptor 7y ago
It seems like the advantage of a CVT only really apply to internal combustion engines since they can only really go from about 500 to 8,000 rpm, and in that range they only have peak power or peak efficiency in small ranges. EV motors can go from 0 to 18,000 rpm.

aidenn0 7y ago

FWIW the original Tesla roadster was also a 2 speed, but they dropped the gearing as soon as they could meet their original top-speed without it.

rconti 7y ago
Yeah, and it was apparently prone to breaking (I learned this from Googling just now). I was pretty sure I drove a 2-speed Roadster back in the day, but wanted to confirm that actually made it to production -- it did. (The Roadsters I drove were Tesla-owned but I'm pretty sure they were full production models). The more things change, the more they stay the same. I remember Tesla being laughed at for this whole overpriced roadster thing, then because their transmissions were breaking, then because the 'fix' was to produce a "crippled" 1-speed car because they couldn't figure out how to make a transmission that didn't break. And now, 10 years later, I own a 1-speed one, and, miraculously, the whole thing works on a real sedan, not just a kit car.

gleglegle 7y ago

It's a little surprising that even with a two-speed Gearbox the Taycan has neither better range nor low range 0-60 acceleration than the Tesla P100D (which has the same size battery). Obviously spec comparisons aren't the whole story and the handling and high-range acceleration may be better on the Taycan. Looking forward to seeing more comparisons and already glad to see more EV models in this category. Edited incorrect comment about top speed.

milkytron 7y ago
According to the article: > It’s programmed to shift between its two speeds at 43 mph, though the computer can be programmed to make the change at different points based on the route, topography, or the distance the driver hopes to cover before plugging in. I wonder if that shift point has anything to do with the slower acceleration. I'd imagine it would make a small difference. As for the top speed, I believe Tesla is limited to 155mph and the Taycan is reported to be limited at 161mph. So the Taycan is actually faster, but I'm not sure how much it matters since both are limited by the software.
- minhazm 7y ago
  Model S top speed is 163 mph.
Mikeb85 7y ago
Porsches have never really been about straightline speed. Always about overall performance and a sports-car feeling. I'm guessing they optimized things like power, gearing and weight placement to offer good acceleration through a range of speeds with amazing handling and decent range at speed.
- rconti 7y ago
  True, and the Taycan may well be a better car in many ways. But a discussion of the gearbox has nothing to do with handling or sports car feeling. I'm wondering what we're missing here. 5% efficiency improvement at high speeds isn't anything to write home about today. The transmission is a known quantity -- it's just gears, it won't get more efficient as they develop it. The efficiency of the whole system (battery/drivetrain/regen/motor/aero/etc) can be optimized quite a bit going forward, but if the 2-speed transmission will only ever get us a 5% increase, I'm not sure it's worth the added weight and complexity. Obviously Porsche knows what they're doing, and it may be about thermal management on the Autobahn more than about outright efficiency, but I'm skeptical. If this were 2010 I'd say "yeah, obviously Porsche knows something about building a real sedan that you can take on a real highway trip, Tesla has no idea what they're doing". But, having produced actual sedans that actually work, and Porsche going with a more complicated system for 5%.. I don't know what I'm missing.

elihu 7y ago

Seems logical. I think most manufacturers have just decided that they'd rather use an over-sized motor than deal with a transmission, but if you're willing to tolerate a more complicated drive-train you get more usable power with less weight. Using a transmission might get weird if you have multiple motors, though. For instance, it would be odd to have the front wheels in one gear and the rear wheels in a different gear, or the right rear wheel in a different gear than the left rear wheel.

jameskilton 7y ago
From what I've read, the AWD versions of the Model 3 (possibly others) actually do this (different ratios in the front and back). As the article says, Tesla had a hard time building a transmission that wouldn't tear itself apart under the torque of the electric motors. So, they put the front and back motors at different ratios. The back motor is used at lower speeds, and the front motor kicks in at higher speeds.
- rconti 7y ago
  I'm not sure about the higher speeds vs lower speeds thing. Anyway, Tesla knows the gear ratios in both units, they can apply power as necessary to get the exact torque split the computer wants.
- elihu 7y ago
  That makes sense for fixed-gear setups; I guess they just have to make sure that the lower-geared motor can spin at high enough RPM that it's not limiting the overall maximum speed. (Or perhaps they can use a freewheel mechanism, but that defeats using that motor for electronic braking.) Having multiple motors each with their own switchable-gear transmission on the other hand might get hard to justify in terms of complexity.

AgloeDreams 7y ago

As I understand it, this gearbox type is key on Porche's intent to make it able to maintain performance over use rather than overheat, notably it improves acceleration and efficiency at high speed. I would expect the Taycan to use less energy to maintain 150mph.

johnvanommen 7y ago
Ah, that makes sense. So that it can cruise at high speeds efficiently.
nraynaud 7y ago
don't you have a ton of cooling air at 150mph?
- AgloeDreams 7y ago
  It's about efficiency at various speeds, plus having to intake more air to cool more things increases drag, the best way to improve cooling performance is to improve power use in the first place.

mprovost 7y ago

Interesting fact about ZF: it was founded in 1915 to make gearboxes for zeppelins.

johnvanommen 7y ago
TIL: "ZF Friedrichshafen is more than 90% owned by the Zeppelin Foundation, which is largely controlled by the town of Friedrichshafen."

baybal2 7y ago

Direct drive BLDCs have enough torque to drive anything under 1t. A split torque design doubles that to 2t. Tiny Chinese EVs have no problems with autobahn speeds for any amount of time.

jaclaz 7y ago

Once upon a time there were cars with a "normal" 4 speed (+reverse) gearbox and an added "overdrive" box (that if I recall correctly could only be used in 3rd and 4th gear), surely there were a few Triumph's and some Volvo station wagons, they had a button/switch on the gear stick that activated it electrically. https://en.wikipedia.org/wiki/Overdrive_(mechanics) https://en.wikipedia.org/wiki/Overdrive_(mechanics) This device (with all the possible evolutions in these 30 or 40 years) sounds a lot like this "overdrive" box.

kwhitefoot 7y ago
Loads of cars had an overdrive and it made a significant difference to fuel economy at high speed. I think the difference here is that the Taycan has a kind of automatic gearbox that can operate while under hard acceleration whereas, as far as I remember, you only pushed the overdrive button when you had reached cruising speed.
- jaclaz 7y ago
  Yes, that is part of the evolutions I mentioned, what I meant essentially was saying that a two speed gearbox (electrically/hydraulically operated) reminds me more an overdrive box (which is actually a two speed gearbox electrically/hydraulically operated) than an actual 4/5/6 speed manual or automatic gearbox. The actual use of the old overdrive was to lower revs of the engine (please read as save fuel) at a given speed, or (I know, not the actual intended use) to increase top speed, which is exactly what the new Taycan gearbox seemingly is used for (automatically, not manually, of course). I remember a diesel Volvo station wagon (must have been a volvo 240 or 244) where in order to overtake someone at 120-130 kmh, the procedure was: 1) turn A/C off 2) accelerate as much as possible in 4th gear 3) push the override button that gave just a little more speed.

nickhalfasleep 7y ago

In dual-motor (front, rear) Tesla vehicles, each motor is on a different gear ratio for optimal power bands.

adrianmonk 7y ago
I wonder if this is part of why their dual-motor models get better range. I could see it being better for regenerative braking, too.
- robotresearcher 7y ago
  Double the regenerative braking is why they get better range, I bet, despite being heavier.
  - kwhitefoot 7y ago
    The two motors in a Model S are different ratings. It seems that at cruising speed the car can choose the most efficient one to use and let the other one 'freewheel'. Two motors probably gives better control over regen and certainly over braking but the regen rate seems to be determined by the battery, inverter, and design decisions. In my 2014 Model S 70D the maximum regen is about 50 kW, at least that's what the display shows, but the motors can develop at least 250 kW. I suspect it is also limited for safety reasons, 250 kW of braking would give deceleration of about the same magnitude as the maximum acceleration. At 100 kph (27.8 m/s) the car has an energy of about 1.62 MJ so at 250 kW it would come to a stop in 6.5 seconds. Actually my car does 0 to 100 kph in about 5.6 seconds so it clearly produces more than 250 kW. Sorry for rambling on, your comment set me thinking and then I just had to check my working.
- adrr 7y ago
  Not sure on the S or X but my model 3 AWD has less range than RWD. AWD is quicker by 10%.
  - driverdan 7y ago

nraynaud 7y ago

just to be sure: should I be in awe in front of a 2 speeds automotive gearbox from a 100 years old manufacturer? it's been a few minutes and I still don't feel the tingling.

kazinator 7y ago

> Multispeed transmissions must be robust to deal with the massive amounts of torque that electric motors can generate in a very short period of time, says Shashank Sripad, a mechanical engineer also from Carnegie Mellon. Put a manual clutch on it; problem solved. Manual boxes can be built strong. Then make it at least a 3 speed so there is a decent H pattern there from the stick user's perspective, and so that the ratio isn't so large (it's like around 2X change¹, supposedly! That means the motor's RPM has to drop by by half on upshift and double on downshift.) 3 speeds could use a 1.44 step. 1 3 | | +-- | \ 2 R = V/I --- 1. Source: this article claims the gears are 16:1 and 8.05:1. https://jalopnik.com/an-extremely-detailed-look-at-the-porsche-taycans-engin-1837802533 https://jalopnik.com/an-extremely-detailed-look-at-the-porsc...

GhostVII 7y ago
If you put a manual gearbox in it, I bet a single bad shift would tear it apart with all that torque at low RPM. Also would probably kill the clutch unless you are a really good driver, and it is hard to shift when you can't hear the engine RPM. And I don't think manual gearboxes are any stronger than a well built automatic but I have nothing to back that up except intuition.
- kazinator 7y ago
  > it is hard to shift when you can't hear the engine RPM. A third-rate hardware tinkerer could come up with a circuit that makes a motorboating sound from a speaker at the engine RPM. That could be heard just during shifting activity, like when the clutch is out. > Also would probably kill the clutch. It would require a special clutch design. The clutch is not needed when starting, of course, because since the motor can generate torque right from zero RPM, the transmission can be engaged. A clutch mechanism needed when changing gears due to the mismatch in speeds that needs to be bridged. The existing two-speeder must have something serving as a clutch, just not a manually operated one. Speaking at torque at zero RPM; can't that be modulated down somehow? Surely there must be some way of managing the motor to bring in torque gently. This must be happening already, right? I mean, electric cars don't burn rubber each time they get moving. > I don't think manual gearboxes are any stronger than a well built automatic That's easy; just define the requirements for "well built" so that it is so, and don't care about weight, size, and other things. The automatic transmission from a bus is probably stronger than the manual in an econobox car.

phkahler 7y ago

Aside from not providing much of any performance benefit, this will introduce difficulty coordinating regenerative braking through the shift point. One of my former employers had a group trying really hard to make a 2-speed for EVs make sense. It just doesn't. If there is an efficiency gain, it's probably better to throw the extra money and weight into the motor. An exception might be if you want to cruise at 120+ mph for long distances, but that's not realistic.

youeseh 7y ago
Which part of cruising at 120+ mph for long distances is not realistic?
- NDizzle 7y ago
  Long distances?
- sdfswfsafaswf 7y ago
  1. outside Germany, cops 2. power scales as v^3 destroying range.
  - Gibbon1 7y ago
    We shouldn't lose sight of #3. 3. This is a toy we're talking about here.
- lazyjones 7y ago
  I eagerly await to see the Taycan's range at 120+ mph. evcalc.ch suggests it would be around 164 Km for 200 Km/h (Turbo S).
GhostVII 7y ago
Why don't you think there will be much performance benefit? The Porsche taycan is much faster accelerating than any Tesla at high speeds, probably due to the two speed gearbox. I don't think it is an efficiency thing, electric motors just start loosing power after a certain rpm, and a gearbox helps with this.

woodandsteel 7y ago

According to the article, two-speed transmissions can increase range about 5%. That is important because batteries are so expensive. However, battery prices are falling rapidly. They dropped 35% in 2018 alone. That being the case, I am guessing most ev manufacturers will stick with single-speed powertrains, and focus their technological efforts elsewhere.

Whatarethese 7y ago

Currently there is no reason to put transmissions into EV's. More money should be put into the improvement of electric motors and battery tech. People care about range and reliability. While acceleration is awesome, Tesla can already achieve sub 2.5s 0-60 which is more than most anyone can handle. Adding a transmission to an EV just adds one more thing to fail and replace fluid every few years.

compiler-guy 7y ago
Are saying that Porsche--which is spending billions of dollars on the Taycan and its transmission--is doing this for no good reason? "People care about range and reliability."--Certainly some, perhaps most people, do. And Tesla serves that market very well. But that isn't Porsche's market. Porsche's target market cares a lot about handling, and performance in track-like conditions.
- Dylan16807 7y ago
  > Are saying that Porsche--which is spending billions of dollars on the Taycan and its transmission--is doing this for no good reason? Yes, they are. They are saying that "better on a track" is a bad reason, and "it makes more money" is a bad reason. That is not a claim that Porsche is incorrectly engineering to reach their goal, or doing anything unprofitable. It's an opinion.
  - GhostVII 7y ago
    In what way is "better on track" a bad reason? Lots of cars have features which are only really useful on a track, are all of these cars needlessly complex?
    - Dylan16807 7y ago
      A lot of people would say yes, and I would not call them objectively wrong to have that opinion.
  - compiler-guy 7y ago

compiler-guy 7y ago

The level of hubris here is pretty high. "No reason"? "No performance benefit"? Porsche is spending billions of dollars to bring a very high performance track-focused sports-sedan to the market. Hundreds of extremely good engineers are getting paid millions of dollars to figure this problem out. I'm sure the transmission is a giant set of engineering tradeoffs (what project isn't), and maybe it won't work out and will end up being the wrong solution. But it can't be so obvious that random Joe-and-Jane HackerNews know the answer off the top of their heads and Porsche doesn't after all the resources it has spent to figure out the problem.

navigatesol 7y ago
There are people on this site and others that truly believe Elon Musk is the smartest engineer on the planet, and by definition his technology is always the best.
- deleted 7y ago
  [deleted]
- erikpukinskis 7y ago
  Please keep your conversations with imaginary people to yourself. There are actual comments here from actual people you can respond to if you’re interested in participating.
- Gibbon1 7y ago
  Well certainly. But behind that guy is a lot of compentent and professional engineers and techs doing the actual work.
gleenn 7y ago
I understand your sentiment. I'd like to add the fact that the original Tesla was a two-speed, or perhaps it was the original design for the Model S, but they scrapped it for simplicity IIRC.
- ztjio 7y ago

p1mrx 7y ago

> comes mated to a motor with a maximum power rating of 140 kW Is that a typo? The Chevy Bolt and Hyundai Kona both have 150 kW motors, and Teslas start above 200 kW.

STRML 7y ago
They don't have any actual inside information about the Taycan, so they switch to talking about the ZF transmission.

ravedave5 7y ago

Porsche has to have reasons for using a gearbox but I don't think this article espouses them. The points they hit on are where Tesla's as good or better, so there must be other good reasons.

userbinator 7y ago

Many years ago I remember reading about EV conversions, and besides direct drive or keeping the existing multispeed (manual) transmission, one of the other relatively popular options was a Chevrolet Powerglide with the torque converter removed. This is a two-speed automatic from the 1950s that's known for being simple and very strong, and remains quite popular for drag racing. I suspect its popularity for EV conversions also arises from being able to handle the huge amount of torque an electric motor can exert, and the better performance of 2 speeds, so it's interesting to see Porsche also choosing a 2-speed auto for its EV.

FullyFunctional 7y ago

What a load of bullshit. The article is making a merit out of a clutch to cover for their failing. I had to stop reading after ridiculous statements like “that 5 percent range improvement can save significant money as battery capacity” - riiiight it can save ... 5%. I’d rather pay more for the battery and save of the maintenance down the road. Serious Wired, how much did they pay you for this?

rukuu001 7y ago

I'm amazed they spent all that R&D loot and then called it 'Taycan' - I can't decide if it sounds more like 'toucan' or 'trashcan'. FWIW the Wikipedia article[0] on the car has this to say about the name: > The name Taycan, roughly translates from Turkish as "lively young horse" in reference to the steed of the Stuttgart coat of arms on the Porsche crest. [0] https://en.wikipedia.org/wiki/Porsche_Taycan https://en.wikipedia.org/wiki/Porsche_Taycan